Convert triggers::module_t::detect_memory_access_match to std::optional

Goal is to remove match_result_t.fire field to eliminate dont-care
fields when fire=false.

riscv/mmu.cc

@@ -157,18 +157,18 @@ void mmu_t::check_triggers(triggers::operation_t operation, reg_t address, std::
   if (matched_trigger || !proc)
     return;
 
-  triggers::match_result_t match = proc->TM.detect_memory_access_match(operation, address, data);
+  auto match = proc->TM.detect_memory_access_match(operation, address, data);
 
-  if (match.fire)
-    switch (match.timing) {
+  if (match.has_value())
+    switch (match->timing) {
       case triggers::TIMING_BEFORE:
-        throw triggers::matched_t(operation, address, match.action);
+        throw triggers::matched_t(operation, address, match->action);
 
       case triggers::TIMING_AFTER:
         // We want to take this exception on the next instruction.  We check
         // whether to do so in the I$ refill path, so flush the I$.
         flush_icache();
-        matched_trigger = new triggers::matched_t(operation, address, match.action);
+        matched_trigger = new triggers::matched_t(operation, address, match->action);
     }
 }
 

riscv/triggers.cc

@@ -331,11 +331,11 @@ bool module_t::tdata2_write(processor_t * const proc, unsigned index, const reg_
   return true;
 }
 
-match_result_t module_t::detect_memory_access_match(operation_t operation, reg_t address, std::optional<reg_t> data) noexcept
+std::optional<match_result_t> module_t::detect_memory_access_match(operation_t operation, reg_t address, std::optional<reg_t> data) noexcept
 {
   state_t * const state = proc->get_state();
   if (state->debug_mode)
-    return match_result_t(false);
+    return std::nullopt;
 
   bool chain_ok = true;
 
@@ -357,7 +357,7 @@ match_result_t module_t::detect_memory_access_match(operation_t operation, reg_t
 
     chain_ok = result.fire || !trigger->get_chain();
   }
-  return match_result_t(false);
+  return std::nullopt;
 }
 
 match_result_t module_t::detect_trap_match(const trap_t& t) noexcept

riscv/triggers.h

@@ -186,7 +186,7 @@ public:
 
   unsigned count() const { return triggers.size(); }
 
-  match_result_t detect_memory_access_match(operation_t operation, reg_t address, std::optional<reg_t> data) noexcept;
+  std::optional<match_result_t> detect_memory_access_match(operation_t operation, reg_t address, std::optional<reg_t> data) noexcept;
   match_result_t detect_trap_match(const trap_t& t) noexcept;
 
   processor_t *proc;